Allow U-Turns based on turn:lanes reverse

[rKsanu2MMYvypWePtQWM]

🐞 routing report

Routing engine

• [x] OsmAnd's in-app offline routing
• [ ] Any online routing provider (YOURS, openrouteservice, OSRM, etc.)

Routing Profile

Car

Start and end points

54.91344N 23.91167E to 54.91188N 23.90998E and 54.91775N 23.91262E to 54.91695N 23.91307E

Actual and expected routes

1st option has a dedicated U-turn point under the bridge (has one of the turn:lanes tagged as "reverse" as an indication) 2nd option is just a regular intersection with a left turn so it should see that a U-turn is possible

Is this a regression?

Unknown ## 🌍 Your Environment **OsmAnd Version:**

4.2.7 Android

**Device and Android/iOS version:** 12 LineageOS **Maps used (online or offline):**

• [x] Offline maps offered within the OsmAnd app for download.
• [ ] Online (tile / raster) maps

Anything else relevant? Perhaps OsmAnd looks for different tags to do a U-turn?

[Zirochkabila]

Reproduced

1st example https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=54.91334%2C23.91165%3B54.91179%2C23.90992#map=17/54.91298/23.91156 correct route - 478 m https://osmand.net/map?start=54.913503%2C23.911690&end=54.911896%2C23.909973&mode=car#17/54.91448/23.91061 incorrect - 2.4 km, cost 352

2d example https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=54.91827%2C23.91313%3B54.91725%2C23.91308#map=17/54.91739/23.91283 correct, (not sure) - 552 m https://osmand.net/map?start=54.917727%2C23.912666&end=54.916931%2C23.913063&mode=car#16/54.9156/23.9107 incorrect - 2.7 km, cost 370

map U-Turns

[sonora]

We have a notable number of open issues involving u-turns https://github.com/osmandapp/Osmand/issues?q=sort%3Aupdated-desc+u-turn+is%3Aopen, reporting both too many (partly illegal) as well as too few (either ignoring explicit possibilities as reported here, or ignoring potential possibilities like when ou are on a wide open road in the desert with no traffic in sight and would certainly turn if your nav only told you that's shorter).

Hence I think the topic deserves an investigation beyond just this issue alone.

[rKsanu2MMYvypWePtQWM]

@Zirochkabila actually the second example does not route properly thru OSM.org OSRM and OSM.org GraphHopper ignores "only straight on" restriction and does the U-turn where it's not allowed. The correct place is on the intersection of Jonavos g. and Salako g.

[rKsanu2MMYvypWePtQWM]

We have a notable number of open issues involving u-turns https://github.com/osmandapp/Osmand/issues?q=sort%3Aupdated-desc+u-turn+is%3Aopen, reporting both too many (partly illegal) as well as too few (either ignoring explicit possibilities as reported here, or ignoring potential possibilities like when ou are on a wide open road in the desert with no traffic in sight and would certainly turn if your nav only told you that's shorter).

Hence I think the topic deserves an investigation beyond just this issue alone.

I was actually surprised that there were no threads about not enough u-turns when researching this topic. seems like there has to be some changes made...

[sonora]

In a lot of cases, whether a U-turn is feasible or not is hard to discover from static map data, it depends on ground truth, traffic, etc. Years ago we used to have a hint "Please make a U-turn when possible" if we discovered movement in the opposite durection of where the best route would actually go.While that gave you a definite hint that turning around would be best if feasible without risk, it also unsettled a lot of users in situations where it was impossible to turn, thinking "What do I do now?". I think eventually we settled to err on the side of safety and rather routed users along a detour than making them aware that u-turning would be shortest...

[rKsanu2MMYvypWePtQWM]

In a lot of cases, whether a U-turn is feasible or not is hard to discover from static map data, it depends on ground truth, traffic, etc. Years ago we used to have a hint "Please make a U-turn when possible" if we discovered movement in the opposite durection of where the best route would actually go.While that gave you a definite hint that turning around would be best if feasible without risk, it also unsettled a lot of users in situations where it was impossible to turn, thinking "What do I do now?". I think eventually we settled to err on the side of safety and rather routed users along a detour than making them aware that u-turning would be shortest...

For random intersections this seems fine, however dedicated places for turn-arounds should be considered.

Also, when road is made out of two one-way ways, OsmAnd will route thru such U-turns because it can't tell that it's the same road and not just two left turns right after another. If such cases are allowed, then u-turns on roads made out of a single way should too...

[vshcherb]

I doubt these are correct routes. So it's better to route as it is then take that risk

[rKsanu2MMYvypWePtQWM]

I doubt these are correct routes. So it's better to route as it is then take that risk

Random U-turns I understand, but turning around at the designated spot should definitely be considered. The first example is exactly why the dedicated turn-around place was made in the first place.

[vshcherb]

Indeed in reality there is a lane and it's possible, I would definetely remap it somehow to make it clear. It has turn:lanes=reverse||| but that's the only indication.

https://help.openstreetmap.org/questions/37870/how-to-map-u-turn-roads

[rKsanu2MMYvypWePtQWM]

Indeed in reality there is a lane and it's possible, I would definetely remap it somehow to make it clear. It has turn:lanes=reverse||| but that's the only indication.

https://help.openstreetmap.org/questions/37870/how-to-map-u-turn-roads

There really isn't a proper way to tag U-turns in OSM. The turnlanes tag seems to be the only way to indicate anything when the road is made out of a single way and not two parallel ways.

[vshcherb]

Yes, I agree you can't put any tag on the node where it should be related to the node (point) not to the way. It's a bit pity of course relying on the lanes looks fishy but probably that the only way to implement it right now.